Your motherboard is 4+1 phases. I wouldn't overclock if i were you. And if you don't want to OC then don't get the 2500k.
Also get a 6950 instead or hop higher to 570.
8giga of low profile and if you are not interested in OC and SLI/Xfire your PSU is an overkill, a 500watts will do nicely.
So, here are my suggestions to you:
Keep the mobo, get a i5 2400
6950 1gb the cheapest you find
8gb of 1600mhz ram, the cheapest credible you find (go high profile if you wish)
toss the cooler, 2400 doesn't need it.
500-550watts from a solid psu.
2400 is not unlocked processor, meaning you can't overclock it (well you can but it is harder than the k versions). You don't wish to OC so there is no need for an unlocked processor. Also no OC means no aftermarket cooler which saves you some money.
8giga is the norm for gaming and you will see difference between 4gb.
The price difference is like 25$, no reason not to go for it as there ARE benefits. Between 8 and 16 though, there aren't any. Thus 8 is the norm and what every gamer with a quad core should get.
Also while speaking about gaming, difference between 2400 and 2500k can't be felt. More insight here: http://www.tomshardware.co.uk/gaming-cpu-overclocking,r... and on the next page where they talk about the 2500k.
GTX 560ti mostly trades blows with the 6950. The 1GB version under-performs the reference 560ti in most games while outperforming in some, whereas the 2GB version mostly gets the better of the 560ti though it still depends on the game you play - GTX 560ti vs. 6950 2GB
EDIT: Getting the 2GB version may also give you the option to flash it to a 6970, though I won't be betting on that. And in any case, AMD might be, by now disabling the extra shaders in 'em for good (substrate instead of the VGA BIOS).
It also depends on the manufacturer. I have the OC 6950 1gb Gigabyte that will outperform most 2gb flashed to 6970 or not.
I agree that if the money can get you there you should get the 570 but it all depends on your resolution. If you don' have a 27" or more monitor any will do for a long time
ATTENTION: The gigabyte i mentioned is 11"